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L The Croonian lecture on the Arrangement and tnechanical 
Action of the Muscles of Fishes. By Anthony Carlisle, Esq, 

JL « JL v« Kj h 4( • «•«/» AJ a 

Read November 7, 1805* 

It was my intention to have continued my physiological 
inquiries on the phenomena of muscular motion, by a series 
of chemical experiments ; and to have communicated the 
result, when duly matured, to the Royal Society. But an un- 
expected request, made at a late period, for the Lecture of the 
present year, obliges me to defer those researches, and to 
limit the investigation of the subject I have chosen/ 

The application of the motive organs of animals has already 
furnished examples of general utility by increasing our know* 
ledge of mechanical powers ; and the cultivation of this study 
promises still further improvement. 

The muscles of fishes are of a very different construction 
from those of the other natural classes. The medium in 
which these animals reside, the form of their bodies, and the 

mdcccvl B 

% Mr. Carlisle's Lecture on the Arrangement 

instruments employed for their progressive motion, give them 
a character peculiarly distinct from the rest of the creation. 
The frame- work of bones or cartilages, called the Skeleton, 
is simple ; the limbs are not formed for complicated motions, 
and the proportion of muscular flesh is remarkably large. 
The muscles of fishes have no tendinous chords, their in- 
sertions being always fleshy. There are, however, semi- 
transparent, pearly tendons placed between the plates of 
muscles, which give origin to a series of short muscular fibres 
passing nearly at right angles between the surfaces of the 
adjoining plates. Lewenhoeck* appears to have overlooked 
these tendons, and the numerous vessels, which he describes 
in the interstices of the muscular flakes, I have not been able 
to discern. 

The motion of a round shaped fish, independent of its fins, 
is simple ; and as it is chiefly effected by the lateral flexure of 
the spine and tail, upon which the great mass of its muscular 
flesh is employed, whilst the fins are moved by small 
muscles, and those, from their position, comparatively but of 
little power, I shall only describe in detail the arrangement 
and application of those masses, which constitute the principal 
moving organs. 

For this purpose a well known fish, the cod/f has been 
selected as a standard of comparison for the muscles of other 
fishes, there being a conspicuous resemblance among them 


The pairs of fins have been considered as analogous to 
feet, but they are only employed for the purposes of turning, 
stopping, altering the position of the fish towards the horizon^ 

* Phil, Trans, Vol, XXXI. p, 190.. f Gadus Morhua of £i-nnjbuju 

and mechanical Action of the Muscles of Fishes, 3 

and for keeping the back upwards. The single fins appear 
to prevent the rolling of the body, whilst the tail is employed 
to impel it forward. 

Each of those fins, which are in pairs, is capable of four 
motions, viz. of flexion and extension, like oars, and of ex- 
panding the rays, and closing them. 

The extension of the whole fin is performed by a single 
radiated muscle, which is often supplied with red blood : the 
antagonist is of a similar character. The great power of 
the extensor muscle (Vide Plate I. a, a,) shews how strongly 
it is required to act when employed to stop suddenly the pro- 
gressive motion. A series of intervening muscles expand and 
close the rays. 

In the act of extending the fin the interosseal muscles are 
passive. It is advanced forward edgeways and closed ; but 
during its flexion, the rays are expanded, striking the water 
with its broadest surface : this action assists the tail in turning 
the fish. In the effort to stop, these fins are strongly retained 
at right angles with the body, by the force of the extensor 
muscles, the rays are expanded, and the effect is assisted by 
the tail turning laterally with its broadest surface forward. 

The single fins, for the expansion and contraction of their 
rays, are furnished with two sets of muscles ; one of which is 
situated at their roots, and lies oblique; (bbbbb) the other, 
parallel with the spines, to which the rays are articulated (cc.) 
The fin has also a lateral motion, by which it is occasionally 
drawn out of a straight line ; and by the co-operation of 
these muscles on both sides, it is kept steady whilst the body 
of the fish is turned oblique in swift motion, or in eddies. 

B 2 

4 Mr. Carlisle's Lecture on the Arrangement 

When placed near the tail, the single fins seem also to aid 
the effect of that instrument by increasing its breadth. 

The tail is the principal organ of progressive motion, and 
Its actions are performed by the great mass of lateral muscles. 
There are a series of short muscles for the purpose of chang- 
ing the figure of the tail fin, which arise from the spine and 
coccyx, and are attached to the rays immediately beyond their 
joints: ( dd): their action is to expand the rays, and by par- 
tial contractions to alter the lateral position of the fin. Slender 
muscles are placed between the several rays, (ee,) whose 
office is to converge them previous to the stroke of the tail. 

The muscles situated on the head are those, which act on 
the membrana branchiosiega, the under jaw, os hyoides, fauces, 
and the globe of the eye. 

In order to determine the effect of the fins on the motions 
of fishes, a number of living dace,* of an equal size, were put 
into a lare;e vessel of water* The pectoral fins of one of these 
fishes were cut off, and it was replaced with the others, Its 
progressive motion was not at all impeded; but the head 
Inclined downwards, and when it attempted to ascend, the 
effort was accomplished with difficulty. 

The pectoral and abdominal fins were then removed from 
a second fish. It remained at the bottom of the vessel, and 
could not be made to ascend. Its progressive motion was not 
perceptibly more slow; but when the tail acted, the body 
shewed a tendency to roll, and the single fins were widely 
expanded, as if to counteract this effect. 

From a third fish, the single fins were taken off. This 

* Cyprinus teitciscus* 

and mechanical Action of the Muscles of Fishes. 5 

produced an evident tendency to turn round, and the pectoral 
fins were kept constantly extended to obviate that motion. 

From a fourth fish, the pectoral and abdominal fins were 
cut off on one side, and it immediately lost the power of 
keeping the back upwards. The single fins were expanded, 
but the fish swam obliquely on its side with the remaining 
pectoral and abdominal fins downwards. 

From a fifth fish, all the fins were removed. Its back was 
kept in a vertical position, whilst at rest, by the expansion of 
the tail, but it rolled half round at every attempt to move. 

From a sixth fish, the tail was cut off close to the body. 
Its progressive motion was considerably impeded, and the 
flexions of the spine were much increased during the endea- 
vour to advance : but neither the pectoral nor abdominal fins 
seemed to be more actively employed. 

From a seventh fish, all the fins and the tail were removed. 
It remained almost without motion, floating near the surface 
of the water, with its belly upward. 

These experiments were repeated on the roach,* the 
gudgeon,^ and the minnow, £ with similar results. 

The muscles of fishes differ materially in their texture 
from those of other animals: they are apparently more 
homogeneous, their fibres are not so much fasciculated, but 
run more parallel to each other, and are always comparatively 
shorter. They become corrugated at the temperature of 156 
of Fahrenheit, when their tendinous and ligamentous attach- 
ments are dissolved, and their serous juices coagulated. 
Under those circumstances the muscles lose their transparency, 
and the lateral cohesion of their fibres is lessened. 

* Cyprinm rutilus. f Cyprinus gobio, { Cyprinus phoxinns. 

6 Mr. Carlisle's Lecture on the Arrangement 

But the mechanical arrangement and physiology of the 
lateral muscles of the body of fishes constitute my present 
object. These parts have already been described in a general 
way by Professor Camper, M. Vicq~d-Azyr, and M. Cuvier, 
to whom I am indebted for much useful information. They 
have been denominated " couches musculaires" by M. Vicg-D- 
Azyr,* and " muscles laterals' 9 by M. CuviER.-f The term 
used by M. Cuvier seems very appropriate for the general 
division or class. But, as the flakes are arranged in distinct 
longitudinal rows, these rows must be considered as orders. 
And, as " couches" appears objectionable, I shall adopt series 
in its stead ; distinguishing each by a word referring to its 
situation in the animal, viz. the dorsal, vertebral, abdominal, 
and ventral series. 

These series are composed of thin masses of muscle, or, as 
they are commonly called, flakes ; which for the most part 
are thicker upon their outward edges, and become wedge- 
shaped towards their interior attachments. Each series is 
separated from the next adjoining by a membraneous parti- 
tion, which is most apparent between the vertebral and 
abdominal series. 

The dorsal series (ff) arises from the back of the head. 
In its course it is terminated on the upper edge by the bones, 
which support the single fins, and a membranous septum : 
at this part the flakes are thin. Its lower margin is bounded 
by the vertebral series, where the flakes become gradually 
thicker. The first flake is composed of longer fibres than the 
rest, and possesses more red blood. Those succeeding it 

* Mem* etrangers de VAcadem* des 8ci» de Paris. Tom. VII. p. iS» et 223^ 
f Lecons d' Anatomic Compare'e. Vol, I, p. 196, 

and mechanical Action of the Muscles of Fishes. 7 

range obliquely backwards. They are all joined together by 
cellular membrane, and shining fasciae, which resemble the 
tendinous expansions in quadrupeds. 

Towards the middle of the fish the flakes are thicker, and 
stand more perpendicular to the surface, becoming oblique 
and thin as they approach the tail ; whilst the intervening 
fasciae are most dense at each extremity. This series consists 
of forty-five flakes, a number corresponding with that of the 
spinous processes to which they are attached, and which does 
not vary with the growth of the fish. 

The muscular fibres constituting each flake, run nearly at 
right angles with its anterior and posterior surfaces, and pa- 
rallel to the length and surface of the fish ; except that their 
posterior extremities incline somewhat inwards. 

As the skull affords the ultimate fixed attachment of this 
series, and its moveable insertions are on the vertebrae, and 
the tail, it follows, that its combined action is to bend the 
whole body and tail towards one side ; or, if the flakes con- 
tract partially, to give it a serpentine motion. To produce 
these effects all the other series co-operate. 

The superior external edges of the flakes of the vertebral 
series (gg) form acute angles with the inferior external 
edges of those of the dorsal series, the apices of which point 
towards the tail : the flakes are larger, but their number is 
the same. The lower margin of this series is bounded by 
the central membranous partition,, which has already been 
noticed to be more conspicuous than the other longitudinal 
divisions, and it apparently admits of greater motion. 

The abdominal series (hh) is composed offtakes similar to 
the preceding. They range towards the tail, forming an angle 

8 Mr, Carlisle's Lecture on the Arrangement 

with those of the vertebral series, the apex of which is pre- 
sented towards the head. They are attached internally to the 
transverse and inferior spinous processes of the vertebrae. 
The ribs are placed in the line of the centre partition, and lie 
"between the flakes. This series arises from a bone which 
borders the opening for the gills, and the pectoral fin, with 
its scapula and muscles, is situated between its foremost 
flakes. Wherever this series encloses the viscera, its flakes 
are shallow, and their thickness internally is not much less 
than at their external superficies. 

Lastly, the flakes of the ventral series (ii ) form acute 
angles with the abdominal flakes, the points of which incline 
to the tail. It is attached anteriorly to the os hyoides, and the 
bone$ of the lower jaw. In its course it is bounded above by 
the abdominal series, and below by a membranous septum , 
within which the inferior single fins arise. The flakes, that 
cover the viscera, are shallow ; and they lie more oblique as 
they approach the tail. Both this, and the last described 
series, have their muscular fibres arranged according to the 
length and figure of the fish. 

Three large superficial nerves (kk) passing longitudinally 
from the head to the tail, in the course of the membranous 
partitions, give off fibrils at right angles, which bend inwards 
between each of the muscular flakes. A larger set of nerves 
are sent from the medulla spinalis, one between each flake, 
the branches of which seem to enter without ramifying there. 
Another small nerve passing from the head, and running 
deep-seated, and close to the dorsal spines, crosses and unites 
with each of the spinal fibrils, and at the junction a remark- 
able body appears ; it is a loose transparent vesicle, about the 

and mechanical Aciiofi of the Muscles of Fishes, g 

size of a millet-seed, containing a white substance like the 
carbonate of lime found in the intercostal ganglions of frogs. 
This vesicle is included within the sheath of the nerve. 

The coats of the blood-vessels are of a delicate texture, 
tod easily ruptured. In order, therefore, to secure them from 
being injured by the violent and sudden actions of the 
muscles, the principal trunks both of the arteries and veins 
are inclosed in osseous canals, formed by the bases of the 
superior and inferior spinous processes ; and their first rami- 
fications lie within grooves in the spines. As they pass out 
to supply the muscles, their branches are immediately subdi- 
vided, so that a considerable vessel soon becomes extremely 

The rate y at which many fishes move through a medium 
so dense as water, is very remarkable ; their velocity being 
scarcely surpassed by the flight of the swiftest birds : and 
although the large proportion of muscles, and their advan- 
tageous application, may partly account for the phenomenon 
yet the power would be inadequate to the effect, if it were 
not suddenly enforced ; as is evident from the slow progress 
of eels, and such fishes as are incapable from their length, 
and flexibility, of giving a sudden lateral stroke. 

But the quickness and force of action in the muscles of 
fishes are counterpoised by the short duration of their powers. 
Those accustomed to the diversion of angling, are aware 
how speedily the strength of a fish is exhausted, for if, when 
hooked, it be kept in constant action, it soon loses even the 
ability to preserve its balance, and turns upon its side, fatigued 
and incapable of motion. This has been vulgarly attributed 
to drowning, in consequence of the mouth being closed upon 

j^dcccvi. C 

10 Mr. Carlisle's Lecture on the Arrangement 

the hook ; but the same effects take place when the hook is 
fastened to the side, or tail. This prostration of strength may 
depend partly on fear, and partly on interrupted respiration^ 
since fishes, when swimming rapidly, keep the membranes 
branchiostegce closed, and when nearly exhausted, act violently 
with their gills. 

The shortness of the muscular fibres, and the multiplied 
ramifications of the blood-vessels, are probably peculiar 
adaptations for the purpose of gaining velocity of action, 
which seems to be invariably connected with a very limited 
duration of it. Such examples form an obvious contrast with 
the muscular structure of slow-moving animals, and with 
those partial arrangements where unusual continuance of 
action is concomitant. 

Since my former communications on the subject of cylin- 
drical arteries,* another instance of their supplying slow- 
moving muscles, which are capable of long continued action* 
has been pointed out to me by Mr. Macartney. It is in the 
muscles, which act upon the feet and toes of many birds, and 
seems to be an adaptation for the long exertion of those 
muscles while they sleep, and also when they alternately 
retract one foot under the feathers to preserve it from the 
effects of cold. 

The muscles of the human body, which perform the most 
sudden actions, have their masses of fibres subdivided by 
transverse tendons, or are arranged in a penmform direction. 
The semi-tendinosus, and semimembranosus of the thigh are 
thus constructed ; the former having its fleshy belly divided 
by a narrow fascia, and the fibres of the latter being ranged 

f Phil, Trans, i&oo, p. 98.— Also 1804, p. 17. 

md mechanical Action of the Muscles of Pishes, 1 1 

in a half-penniform manner. The recti abdominis are also di- 
vided into short masses by transverse tendons, and all these 
muscles are conjointly employed in the action of leaping. 

Perhaps these observations may indicate the reason for 
that diversity in the lengths of various muscles, which act 
together ; thus, organs of velocity are joined with those of 
power, and mutually co-operate to produce a simultaneous 

Description of Plate I. 

The drawing was made from a cod which had been coagu- 
lated by heat, in a case of plaister of Paris, the skin being 
taken away, and an equal portion of the flakes carefully 
removed from each series, to exhibit their several directions. 
The subject was reduced to the present size by accurate 

aa, Muscles which extend the pectoral and jugular fins. 

bbbbb, Oblique muscles, which erect the rays of the single 

cc, Muscles which depress the rays. 

dd, Muscles which extend the rays of the taiL 

ee, Interosseal muscles, which close the rays* 

ff, The dorsal series of muscular flakes, 

gg, The vertebral series. 

hh, The abdominal series. 

ii, The ventral series. 

kkk, Three superficial nerves which run longitudinally be* 
tween the series of flakes. 

/, Posterior surface of a dorsal flake. 

m, Posterior surface of an abdominal flake f 

is Mr. Carlisle's Lecture on the Arrangement, &c. 

n, Anterior surface of a vertebral flake. 

o, Anterior surface of an abdominal flake. 

The middle portion of the fish from whence the flakes have 
been removed, shews the several directions of them, and also 
their different thicknesses. The spine appears in the chasm. 

Ailcs.TmnsMXi CCC \l.Mate l.p.22 


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